Spin relaxation phenomena in GaAs/AlGaAs quantum wells
Spin relaxation phenomena in GaAs/AlGaAs quantum wells
This thesis presents a study of carrier dynamics in GaAs/AlGaAs quantum wells. Non-equilibrium distributions of spin polarisations were excited and probed in wells grown in (100) and (110) crystal orientations by means of picosecond pulses. This spin polarisation decays exponentially with time and can be understood in terms of a motional narrowing scattering process described by D’yakonov and Perel, concerning the effect of spin splitting of the conduction band creating a fictious magnetic field that acts upon the spin of the electron. These scattering processes can also include electron-electron scattering events that do not contribute to the mobility.
The (110) wells were studied to show the effect of both built in and applied bias on the spin relaxation time. It was thought that this contribution to the mean square precession frequency of the electron would act at right angles to the spin splitting of the conduction band and hence increase the rate of spin relaxation. Calculations were made of the theoretical values of spin relaxation as a function of applied bias and these values were compared with experimental values. It was necessary to assume less than optimum growth conditions in order to account for the discrepancies at low bias. A (110) sample was also investigated for magnetic field dependence in order to derive a value for the momentum scattering time but the results remain inconclusive.
(100) samples were investigated to study the expected occurrence of a minimum in the temperature dependence of the spin relaxation rate, corresponding to the Fermi temperature. This sample was also investigated to study the carrier concentration dependence of the spin relaxation rate. At low biases neutral and negatively charged excitons were seen and deductions were made about their spin relaxation.
University of Southampton
John, Gareth H
81f01aa5-a153-4dd9-8bb2-b2f94565ff8f
2005
John, Gareth H
81f01aa5-a153-4dd9-8bb2-b2f94565ff8f
John, Gareth H
(2005)
Spin relaxation phenomena in GaAs/AlGaAs quantum wells.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis presents a study of carrier dynamics in GaAs/AlGaAs quantum wells. Non-equilibrium distributions of spin polarisations were excited and probed in wells grown in (100) and (110) crystal orientations by means of picosecond pulses. This spin polarisation decays exponentially with time and can be understood in terms of a motional narrowing scattering process described by D’yakonov and Perel, concerning the effect of spin splitting of the conduction band creating a fictious magnetic field that acts upon the spin of the electron. These scattering processes can also include electron-electron scattering events that do not contribute to the mobility.
The (110) wells were studied to show the effect of both built in and applied bias on the spin relaxation time. It was thought that this contribution to the mean square precession frequency of the electron would act at right angles to the spin splitting of the conduction band and hence increase the rate of spin relaxation. Calculations were made of the theoretical values of spin relaxation as a function of applied bias and these values were compared with experimental values. It was necessary to assume less than optimum growth conditions in order to account for the discrepancies at low bias. A (110) sample was also investigated for magnetic field dependence in order to derive a value for the momentum scattering time but the results remain inconclusive.
(100) samples were investigated to study the expected occurrence of a minimum in the temperature dependence of the spin relaxation rate, corresponding to the Fermi temperature. This sample was also investigated to study the carrier concentration dependence of the spin relaxation rate. At low biases neutral and negatively charged excitons were seen and deductions were made about their spin relaxation.
Text
1026844.pdf
- Version of Record
More information
Published date: 2005
Identifiers
Local EPrints ID: 465987
URI: http://eprints.soton.ac.uk/id/eprint/465987
PURE UUID: becc5757-7540-4bb6-8b2a-e75e3df2b741
Catalogue record
Date deposited: 05 Jul 2022 03:53
Last modified: 16 Mar 2024 20:27
Export record
Contributors
Author:
Gareth H John
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics